1. Field of the Invention
The present invention relates to an ink jet recording apparatus having a function as facsimile, a copying machine or a printer, a composite apparatus having these functions, or an ink jet recording apparatus utilized as output equipment for example of a work station.
2. Related Background Art
Ink jet recording apparatuses have been developed and commercialized actively in recent years because of various advantages, and are known in various types such as based on ink discharge utilizing a piezoelectric element or utilizing ink bubbles generated by an electrothermal converting element such as a heat-generating resistor.
In an ink jet recording apparatus of the recording method utilizing the electrothermal converting element, a voltage or current pulse is supplied, in response to the image signal, to said converting element to generate thermal energy, thereby inducing a state change in the ink such as membrane boiling. A bubble is generated by said state change, and ink is discharged toward the recording material by the force of said bubble. The characteristics of bubble generation and discharge of the ink are dependent on the physical properties, for example, viscosity, of the ink, and therefore vary, in general, with the temperature thereof. For this reason, there is provided temperature control means as disclosed for instance in U.S. Pat. No. 4,719,472, for controlling the ink temperature within a certain range.
Also, the state of bubble generation is dependent on the voltage, current and duration of the pulse applied to the electrothermal converting element, so that these parameters are selected at optimum values according to the resistance or the surface characteristics of said electrothermal converting element.
A high image quality can be obtained in a stable manner by controlling the driving conditions in an optimum range as explained above.
However, with the progress of system integration, there is often encountered a situation where the same ink jet recording apparatus is used not only as a printer but also is output equipment of a facsimile apparatus or a copying machine, with respectively different transfer rates of the image signal. For example, an ink jet recording apparatus may have a printer mode in which the image signal is received at every 500 .mu.sec. and a facsimile mode in which the image signal is received at every 10 msec.
Such different receiving rates of the image signal varies the recording speed, thereby also causing a change in the aforementioned optimum driving conditions, so that the conventional recording apparatus is unable to provide stable recorded images.
Also, in the compressed image transmission as in the facsimile apparatus, the above-mentioned difficulty is encountered even for the same receiving rate, as the effective image signal receiving rate varies if the image compression rate is different.